But the most surprising number in the poll is Rubio’s: In June, Rubio was the first-choice candidate among 14% of Republican primary voters, which put him in a close third behind Walker and Bush.

But in the poll released Sunday, Rubio’s support dropped to 5%, putting him in just eighth place.

This has been part of a recent trend for Rubio in national polling. In early May, shortly after he announced his candidacy, he placed second among Republicans with 14.3% support in a Real Clear Politics average of recent polls. With the NBC/Wall Street Journal poll, his average support dipped to just 6%.

Since the Republican primary field is so large, with 16 major candidates in the race, much of the difference among the candidates is within the poll’s margin of error. In the case of the Journal’s recent poll, the-margin-of-error is particularly large — plus-or-minus 6%.

And though multiple polls show his support dipping, there are still some signs that Rubio can make up for lost ground once the field starts to thin.

According to Public Policy Polling, fore example, the Florida senator is still viewed more favourably than most other Republican candidates, though his numbers have fallen since May.

Rubio’s lacklustre poll numbers come as he has attempted to take a somewhat more subtle approach to campaigning.

While rivals like former Arkansas Gov. Mike Huckabee (R), Sen. Ted Cruz (R-Texas), and Trump have lit up the campaign trail with controversial rhetoric, Rubio has been more low-key. He has foregone provocative headline-grabbing statements about his rivals while directing occasional barbs at Democratic front-runner Hillary Clinton and President Barack Obama.